1. Field of the Invention
The present invention relates to a liquid crystal display (LCD), and more particularly, to an LCD having a reflecting region which is formed inside a liquid crystal panel and in which external light can be reflected.
2. Description of the Related Art
A liquid crystal display (LCD) is a thin, flat display device made up of arrays of color or monochrome pixels. Due to its low power consumption, it has been most widely used as displays for battery powered electronic devices in which low power consumption plays a crucial role.
LCDs are categorized as either transmissive, reflective, or transreflective LCDs according to the location of a light source for illuminating liquid crystal (LC). In the transmissive LCDs, liquid crystals are illuminated by a backlight unit (BLU) that is located at the back of a panel.
This type of LCDs are used in applications such as flat panel displays, televisions, personal digital assistants (PDA) or mobile phones which that require high luminance levels.
One of major drawbacks of transmissive LCDs is in their dependence on BLU as an illuminating light source in which major power consumption occurs for the system.
In the reflective LCDs, external light is used as a lighting source for illuminating LCs in the device. The external light reflects off a reflector which is placed at the back of an LC layer. In the reflective LCDs, the absence of an active lighting source such as a BLU for transmissive LCDs significantly reduces the overall power consumption for the system, which mask the reflective LCDs attractive technology in applications such as digital watches and calculators to name a few where low power consumption is of crucial importance.
However, the reflective LCDs are not perfect. Since the reflective LCDs do not have their own built in lighting source such as BLU for illumination, they cannot be used in places that are not surrounded by external light sources, that is, places where there is no external light. In addition, since in the reflective LCDs, the light must pass through the LC layer twice, it suffers from a low contrast ratio compared to the transmissive LCD counterparts.
Many commercially available devices such as PDA or mobile phones in which both low power consumption and high image quality are of crucial importance, take advantages from both reflective and transmissive LCD technologies by combining the two into a single package, which technology is known as transreflective LCD. The transreflective LCDs work by switching modes between a reflective LCD and a transmissive LCD depending on the condition of an external ambient light source in an environment. During the daylight or in places where sufficient ambient light source is present, the reflective LCD mode gets activated, and during nights or in dark environments, the transmissive LCD mode gets enabled.
Although the transreflective LCD technology seems to be the perfect solution, for proper balancing between the need for lower power consumption and high image displaying quality, there are still much more required fine tunings. Since this technology merely combines the two previous versions, reflective and transmissive LCD technologies, the problems that were present in reflective and transmissive LCD technologies are present in transreflective LCD technology. One of the major shortcomings in devices utilizing transreflective LCD technology is poor contrast ratio performance of which trait can trace the reflective LCD technology portion.
This defect may be attributed to the following two processes:                1. The light must pass through the LC layer twice in the reflective LCD.        2. Only a small portion of the external light rays reflecting by the reflector contributes to illumination of the LC layer.        
In the reflective LCD, since light must pass the LC layer twice, the latter of the two above-attributed defects can be improved.
Rays of a component which passes through the LC layer vertically after reflecting off the reflector substantially, contribute to illumination of the LC layer so as to show the excellent contrast ratio performance of rays reflecting off the reflector.
Thus, in order to improve contrast ratio performance, the amount of a component which passes through the LC layer vertically, needs to be increased so as to improve the ratio of rays reflecting off the reflector that substantially contributes to illumination of the LC layer.